1. Field of the Invention
The present invention relates to an adhesive tape attaching method for attaching an adhesive tape to the back side of a wafer having a circular recess on the back side.
2. Description of the Related Art
In a semiconductor device fabrication process, a plurality of crossing division lines called streets are formed on the front side of a substantially disk-shaped semiconductor wafer to thereby partition a plurality of regions where devices such as ICs and LSIs are respectively formed. The semiconductor wafer is cut along these streets by a cutting apparatus to thereby divide the semiconductor wafer into individual semiconductor chips (devices). Prior to cutting the wafer along the streets, the back side of the wafer is ground or polished to reduce the thickness of the wafer to a predetermined value. In recent years, it has been required to further reduce the wafer thickness to about 50 μm, for example, in order to achieve a reduction in size and weight of electric equipment.
However, such a thin wafer is difficult to handling and there is a possibility of damage to the wafer during transportation thereof. To solve this problem, there has been proposed a grinding method in Japanese Patent Laid-open No. 2007-19461, for example. In this grinding method, the back side of a wafer is ground in only an area corresponding to a device area where the devices are formed on the front side of the wafer, thereby forming a circular recess corresponding to the device area and an annular reinforcing portion surrounding the circular recess so as to correspond to a peripheral marginal area surrounding the device area. On the other hand, to ease the handling of the individual devices obtained by cutting the semiconductor wafer, the semiconductor wafer is attached to a dicing tape (adhesive tape) prior to cutting the wafer. That is, in cutting the wafer by using a cutting apparatus, the wafer with the adhesive tape is cut by a cutting blade from the front side of the wafer to the middle of the thickness of the adhesive tape, thereby dividing the wafer into the individual devices in the condition where the individual devices are attached to the adhesive tape. Accordingly, scattering of the individual devices can be prevented even after cutting the wafer.
A method of attaching an adhesive tape to a semiconductor wafer is known in the art (see Japanese Patent Laid-open No. Hei 6-177243, for example). In this method, the adhesive tape is attached to the back side of the semiconductor wafer by opposing the adhesive surface of the adhesive tape to the back side of the semiconductor wafer and sliding a roller on the nonadhesive surface of the adhesive tape. However, there is a possibility of damage to the thin semiconductor wafer by the pressure of the roller. To cope with this problem, there has been proposed a device for attaching a semiconductor wafer to an adhesive tape by the expansion of an elastic member for supporting the semiconductor wafer (see Japanese Patent Laid-open No. 2005-135931, for example).
However, there arises a problem even when such a device is used to attach the adhesive tape to the semiconductor wafer. That is, in a semiconductor wafer having a circular recess formed by grinding the back side of the wafer in only an area corresponding to the device area to thereby form an annular reinforcing portion around the circular recess so as to correspond to the peripheral marginal area surrounding the device area, there is a possibility of damage due to the stress generated at the boundary between the annular reinforcing portion and the circular recess in attaching the adhesive tape.